This invention relates to a hard disk inspection apparatus for inspecting magnetic recording and reproducing characteristics of a hard disk (information storing medium) to be built in a computer or the like.
This type of a hard disk inspection apparatus is already disclosed in Japanese Utility Model Laid-Open No. 17684/1990. This hard disk inspection apparatus simultaneously inspects the front surface and the back surface of a hard disk by dividing the surfaces into an outside magnetic recording area and inside magnetic recording area, respectively, in order to shorten the hard-disk inspection time.
Therefore, two pairs of carriages are arranged at the both sides of a hard disk rotating on the spindle so that they face each other, two magnetic heads are set to the end of one pair of carriages so that they are provided on the front surface and the back surface of the hard disk, and a fine-adjustment magnetic head provided on the surface of the hard disk and a magnetic head provided on the back thereof are set to the other pair of carriages so that the displacement can be fine-adjusted by a micrometer.
In this manner, inspection is performed by four magnetic heads at the same time.
When four magnetic heads are set, an error of, for example, approx. 0.5 mm is produced at the carriage or magnetic head setting position. However, because it is necessary to keep the error within 2 to 3 .mu.m for effective inspection, the fine-adjustment magnetic head is fine adjusted by the micrometer.
This structure prevents the inspection of recording tracks from being neglected or performed twice at the boundary between two divided areas, (outside and inside magnetic recording areas) by fine-adjusting the position of the fine-adjustment magnetic heads when magnetically recording inspection signals in a hard disk by using a magnetic head before reproducing them or when inspection known missing pulse errors, extra pulse errors, positive modulation, and negative modulation with the reproduced signals after erasing magnetic records.
However, the conventional hard disk inspection apparatus can only adjust one magnetic head precisely with one micrometer. In this case, it is possible to adjust the displacement between two magnetic heads arranged on the front surface of the hard disk and that between two magnetic heads arranged on the back surface of the hard disk but it is impossible to adjust the displacement between two magnetic heads for the front surface and the back surface arranged on one carriage.
It is also impossible to adjust the displacement between two magnetic heads each other arranged on both carriages. For example, if a hard disk is inversely set in order to determine the electrical characteristics of one of a pair of magnetic heads, the inspection efficiency is not improved because the initially recorded position becomes unclear.